Carburetor



Jan. 25, 1966 R, E. KALERT, JR 3,231,250

CARBURETOR Filed Aug. 30, 1962 5 Sheets-Sheet l INVENTOR. RALPH E.KALERT JR.

AGENT Jan. 25, 1966 KALERT, JR 3,231,250

CARBURETOR Filed Aug. 50, 1962 5 Sheets-Sheet .2

JNVENTOR. RALPH E. KALE TJR.

AGENT 5 Sheets-Sheet 3 INVENT AGENT Jan. 25, 1966 R, E. KALERT, JR

CARBURETOR Filed Aug. 30, 1962 FIG.5.

RALPH E. KALERT 'JR.

United States Patent C 3,231,250 CARBURETQR Ralph E. Kalert, In, GraniteCity, Ill., assignor to ACE Industries Incorporated, New York, N.Y., acorporation of New Jersey Filed Aug. 30, 1962, Ser. No. 220,405 11Claims. (Cl. 261-41) This invention relates to carburetors, and moreparticularly to a carburetor of the type having a horizontal mixtureconduit and a fuel bowl below the mixture conduit.

Among the several objects of the invention may be noted the provision ofa carburetor of the class described for small internal combustionengines (such as are used on apparatus such as power lawn mowers and thelike) which is of such construction that it may be manufactured at lowcost primarily from sheet metal and molded plastic parts, including asheet metal fuel bowl, a molded plastic bowl cover, and a sheet metaltube which constitutes the mixture conduit of the carburetor; theprovision of a carburetor such as described having a construction which,in simple and economical manner, provides a boost venturi in addition toa main venturi; and the provision of a carburetor such as describedhaving a low speed or idle fuel system, in addition to its high speedfuel system, with provision for adjustment of both the high speed andidle systems. Other objects and features will be in part apparent and inpart pointed out hereinafter.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

FIG. 1 is a plan of a carburetor made according to the invention,showing the carburetor attached to the intake manifold of an internalcombustion engine;

FIG. 2 is an enlarged vertical section taken on line 2-2 of FIG. 1(omitting the intake manifold);

FIG. 3 is a horizontal section taken on line 3-3 of FIG. 2;

FIG. 4 is a plan of the bowl cover per se of the carburetor;

FIG. 5 is an enlarged vertical section taken on line 55 of FIG. -1; and

FIG. 6 is a vertical section taken on line 6-6 of FIG. 2;

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Referring to the drawings, a carburetor constructed in accordance withthis invention is shown to comprise a fuel receptacle constituted by abowl 1 and a cover 3 on the bowl. A mixture conduit 5 extendshorizontally over the cover. Bowl 1 is shown as comprising a circuilarcup, and may be a deep-drawn sheet metal cup. Cover 3 is shown as acircular molded plastic cover having a circular groove 7 in its bottomadjacent its periphery receiving the rim of the cup-shaped bowl with aringshaped gasket 9 in the groove between the rim of the bowl and thecover. Mixture conduit 5 is constituted by a sheet metal tube, and has aflange or collar 11 secured on one end thereof. This has bolt holes 13(see FIG. 3) for reception of bolts 15 (see FIG. 1) to attach thecarburetor to the intake manifold M of an internal combustion engine. Atthe other end of the tube is an air horn 17 which may contain an airfilter (not shown) and which has a cap 19 with a quick detachablebayonet connection 21 to the horn. It will be understood that cap 19 hasopenings in its end face for admission of air to the horn.

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Cover 3 has an integral upwardly extending formation 23 (FIGS. 3, 4 and5) on its top. This extends diametrically across the cover, and isformed with a recess 25 of arcuate shape in transverse cross sectionextending throughout its length. Tube 5 is seated in this recess with agasket 27 underneath the tube. The length of the tube is somewhatgreater than the diameter of the cover and the tube projects at bothends beyond the cover. Cover 3 also has an integral cylindric stud 29extending upward from its center and in integral stud 31 of pearshape incross section (see FIG. 4) extending downward generallycentrally of thecover. Stud 29 extends through a hole 33 (FIG. 2) in the wall of tube 5at the bottom of the latter (there being a registering hole 35 in gasket27), and has a reduced-diameter upper end extension 37 which extendsthrough a hole 39 in the wall of tube 5 at the top. At the inner (lower)end of extension 37, stud 29 has an annular shoulder 41 on which the topof the tube 5 is seated. Shoulder 41 is suitably curved for this purpose(see FIG. 2). A cap nut 43 is threaded on extension 37 to hold thetubein assembly with cover 3 with a sealing washer 45 under the nut.

Stud 29 has a crosshole 47 extending lengthwise of tube 5 adjacent thebottom of the tube. The ends of crosshole 47 are beveled as indicated at49, and crosshole 47 constitutes what may be termed a primary or boostventuri as will be later explained. Stud 31 extends down to the bottomof bowl 3 generally centrally of the bowl, and has a cylindric recess 51which extends up from its lower end nearly to the top of cover 3, with areduceddiameter hole 53 in continuation of the recess extending to thecrosshole 47. Recess 51, toward its lower end, is tapped as indicated at55. Threaded in the lower end of recess 51 is a screw 57 extendingthrough a central hole 59 in the bottom of the bowl 3 and having a head61 engaging a sealing washer 63 which seals against the bottom of thebowl. This holds the bowl and cover in as sembly. Screw 57 is tubular,having a metering orifice 65 at its upper end communicating with atapped bore 67 which opens at its lower end into an enlarged cylindricrecess 69 in the lower end of the screw. A needle valve designated inits entirety by reference character 71 is adjustable in screw 57. Asshown in FIG. 2, needle valve 71 has a stem 73 threaded at its upper endin the tapped bore- 67 of screw 57, extending down through recess 69 andhaving a knurled head 75 on its lower end, and having a needle tip 77movable up and down in metering orifice 65. An O-ring 79 is retained inan annular groove in the stem for sealing recess 69, and a coilcompression spring 81 is provided between the knurled head 75 of theneedle valve and the head 61 of screw 57.

A fuel tube 83 has its upper end pressed in hole 53 and extends downinto recess 51 with its lower end somewhat above the upper end of screw57. The portion of recess 51 above the upper end of screw 57 constitutesa fuel well 84 and fuel is adapted to flow into this well from the bowl3 via a port 85 in stud 31 which communicates with a space around screw57 provided by an annular peripheral groove 37 in the screw 57, ports 89in the screw 57 providing for communication from groove 87 to the spaceWithin screw 57 above the stem 73 of the needle valve, and the meteringorifice 65, with the rate of flow controllable by the adjustment of theneedle valve 71.

Cover 3 is molded with grooves such as indicated at 91, 93, and 97 inFIG. 4, grooves 91, 93, and 97 extendinggenerally lengthwise and groove95 extending crosswise of the tube-seating recess 25. Groove 91 is arelatively shallow groove extending from near the air horn end of therecess 25 (its upstream end) to the region of stud 29 on one side of thelatter. A branch groove 3 91a angles off from groove 91 to the centralvertical longitudinal plane of recess 25, terminating just upstream fromstud 29. Air is adapted to bleed into the groove 91 at its upstream endvia an air bleed hole 99 in tube 5 (see FIG. 3) and a registering holein gasket 27, the remainder of the groove being covered by the gasket27. Air bleeding into groove 91 through hole 99 is adapted to flowthrough branch groove 91a and through a passage 101 to the fuel well 8 1(FIG. 2). Passage 101 angles downward from the end of branch groove 91ain the central vertical longitudinal plane of recess to the well 84.Fuel tube 83 has holes such as indicated at 103 for bleeding airentering well 84 via passage 101 into the tube 83. These holes 103 aremade of such size as appropriately to meter the flow of air into thefuel tube.

Groove 93 is a relatively shallow groove having its upstream endadjacent the downstream end of groove 91,- and extends lengthwise ofrecess 25 in line with groove 91 for some distance, then curves inwardso that its downstream end 93:: is located in the central verticallongitudinal plane of recess 25. At its upstream end, groove 93 has arelatively deep pocket 105 (FIGS. 4 and 6). A passage 107 interconnectsthe downstream end of groove 91 and the upstream end of groove 93.

Groove 95 is a relatively deep groove located immediately adjacent stud29 on the downstream side thereof and extending crosswise of recess 25.Stud 31 has a vertical idle system passage 199 (FIGS. 2, 4 and 6)extending down from groove 95 (on the downstream side of recess 51).This idle passage 199' extends all the way down to the lower end of stud31. Fuel is adapted to enter passage 109 adjacent its lower end via aport 111 (seeFIG. 2) providing for communication from annular groove 87to passage 109. A metering jet 113 is pressed into passage 199 from itslower end, this jet being located just above port 111. An economizerpassage 115 connects grooves 95 and 93, extending between one end ofgroove 95 to the pocket 195.

The wall of tube 5 has a stepped idle port 117 (see FIG. 2) in thebottom registering via a hole 119 in gasket 27 with the downstream end93a of groove 93. Flow through this idle port is regulated by an idleadjusting screw 121 threaded in a tapped hole 123 in the wall of tube 5at the top aligned with port 117. Screw 121 extends vertically downwardthrough tube 5 and has a conical tip 125 at its lower end adjustablymovable, up and down, in port 117 by the turning of screw 121 to varythe effective area of the port 117. Screw 121 has a notched head 127 atits upper end to receive a turning tool. A coil compression spring 129is provided between head 127 and theutop of tube 5.

Groove 97 extends on the side of recess 25 opposite grooves 91 and 93and alongside the stud 29. Air is adapted to bleed into groove 97 at itsupstream end via an air bleed hole 131 in the Wall of tube 5 (see FIG.3) and a registering hole in gasket 27, the remainder of the groovebeing covered by the gasket. Air bleeding into groove 97 through hole131 is adapted to flow through a passage 133 (FIGS. 4 and 6) into groove95, this passage 133 extending from the downstream end of groove 131laterally to the respective end of groove 95.

A throttle shaft 135 extends vertically downward in tube 5 downstreamfrom stud 29, being journaled in holes 137 and 139 in the wall of thetube at top and bottom. Fastened to shaft 135 in tube 5 is a throttlevalve 141 constituted by an elliptical sheet metal disk. Shaft 135 islocated between stud 29 and idle adjusting screw 121, and the throttlevalve 141 is rotatable with the shaft between a closed idle or low speedposition shown in dotted lines in FIG. 3 and the full-open positionshown in solid lines in FIG. 3, the latter being determined byengagement of the throttle valve with the idle adjusting screw 121.Shaft 135 has an arm 142 on its upper end for connection thereto of athrottle-operating linkage.

The wall of tube 5 has an idle air bleed hole 143 iru register with theupstream end of the groove 93 and at corresponding hole in gasket 27 forbleeding air into-2' groove 93 from upstream of the throttle valve 141when: the latter is in the closed idle or low speed position. The* wallof tube 5 also has a hole 14-5 constituting an acceleration port inregister with groove 93 via a corresponding. hole in gasket 27, thisport 145 being located so as to be blocked by the rim of throttle valve141 when the latter is in closed position.

A choke shaft 147 (FIG. 2) extends vertically downward in tube 5upstream from stud 29, being journaled in holes 149 and 151 in the wallof the tube at top and bottom. Fastened to shaft 14-7 in the tube is achoke valve 153 constituted by an elliptical sheet metal disk. The chokevalve is biased toward open position (see FIG. 3) by a torsion spring155 positioned around nut 43, having one end 157 inserted in a hole 159in the tube 5, and its other end 161 engaging a bent operating arm 163at the upper end of shaft 147. Bleed hole 99 is located to her upstreamfrom the choke when the choke valve is closeed; The choke valve swingsclosed in counterclockwise direc tion as viewed in FIG. 3 toa positionindicated by the.- dotted structure 153.

Cover 3 is formed with a nipple 165 (FIGS. 5 and 6)= extending upwardtherefrom at one side of formation 23" for connection of a fuel lineschematically shown at 166 in FIG. 5, for delivery of fuel from a tank168 to bowl 1.- Nipple 165 communicates downward through a port 167'(see FIG. 5) to the upper end of a downwardly opening: cylindric recess169 in the cover. A needle valve 171 has a stern 173 of cruciform crosssection vertically slidable in recess 169. Valve 171 is adapted forengagement on upward movement with the valve seat 175 provided at theupper end of the recess. Valve 171 has a button 177 at its lower endengaging an arm 179 on a float lever 181 pivoted for swinging movementon a horizontal axis underneath the cover 3 and carrying an annularfloat 183 surrounding stud 31. Lever 181 is formed of sheet metal withtwo side ears 185 each having outwardly extending bosses 187 snappedinto corresponding recesses in a pair of lugs 189 extending down fromthe cover for holding the lever and float in pivoted assembly with thecover. Cover 3 is provided with a vent passage 191 for venting to theatmosphere fuel vapors in the bowl 1. Fuel may be fed from tank 168 tothe fitting 165 by means of gravity or by a fuel pump.

With regard to the operation of the carburetor, it will be apparent thata predetermined level of fuel, well above the level of port 85, ismaintained in the bowl 1 by means of the float-controlled needle valve171. During high-speed operation with the throttle 141 open there is amaximum flow of air through tube 5 to the engine. Stud 29 provides aportion of restricted cross sectional area in tube 5 constituting a mainventuri, and passage 47, which extends lengthwise in relation to tube 5and provides a. venturi effect in view of its beveled ends, acts as aboost. venturi for boosting the delivery of fuel. The flow of air aroundstud 29 and through passage 47 is subatmospheric so that fuel is forcedfrom bowl 1 through port 85 and. through the passages in screw 57 tofuel well 84, and. thence through fuel tube 83 to the hole 47 in stud29. Air bleeds into fuel well 84 via air bleed hole 99, groove orpassage 91a and passage 191. This air passes through ports 103 to mixwith the fuel passing upwardly through the fuel tube 83. The flow offuel for high speed operation is metered at orifice 65, depending on theadjustment of the needle valve 71.

With the throttle valve 141 in a closed position, shown by thedotted-line throttle position of FIG. 3, engine manifold vacuum existsdownstream of the throttle valve. Fuel is forced from the bowl throughpassages 85, 89 and 111 into idle passage 199. Fuel flows into passages95, 115, 93. and out the idle port 117. The restriction 113 in passage199 is of a predetermined size depending on the needs of the engine andmeters the solid fuel flowing into the low speed system. Air is bledinto the low speed system through port 131 upstream of the closedthrottle valve 141. This air flows in response to the pressuredifferential on opposite sides of the closed throttle and throughpassages 97 and 133 into groove 95 where it meets the solid fuel beingforced up passage 109. This air tends to vaporize the fuel to form anair and fuel mixture or emulsion and also directs this emulsion throughthe economizer passage 115, which being of a predetermined cross sectionmeters this air and fuel mixture. Additional low speed air is bled intothe low speed system from upstream of the closed throttle through port99 and passages 91 and 107. This air strikes the air and fuel mixturecoming through the economizer passage 115 to lean the mixture and thiskeeps the fuel vaporized. This air also accelerates the fuel and airmixture down passage 93 and out the idle port 117. The screw 12 1 isadjusted to control the amount of fuel and air mixture required forproper low speed operation. The air bleed port 143 may be used tofurther lean out the fuel and air mixture in passage 93, if desired.

As the throttle is opened, in the transition from low speed to highspeed operation of the engine, the throttle valve uncovers port 145. Airsweeping around the edge of the throttle valve is at low pressure andadditional accelerating fuel and air mixture is sucked through port 145to speed up the engine until air flow through the venturi passage 47 canraise fuel into the mixture passage '5. The potional port 143 also isswept by the throttle 141 as it is opened to provide an additional flowof accelcrating fuel and air from passage 93.

The bowl 1, cover 3 and tube 5 are the main parts of the carburetor.Bowl 1 and tube 5 can be made of sheet metal and cover 3 of moldedplastic. Thus, these are all low-cost parts. Assembly of these parts isrelatively simple, involving attaching bowl 1 to cover 3 by threadingscrew 57 through hole 59 in the bottom of the bowl and attaching tube 5to stud 2.9 by threading cap nut 43 on the extension 37 of stud 29.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A carburetor comprising a fuel bowl, a cover on the bowl, a tubeconstituting a mixture conduit extending across the cover on top of thecover, an upper stud formed integrally with the cover extending upwardfrom the cover through holes in the tube wall at top and bottom, meanson the upper end of said upper stud holding the tube in assembly withthe cover, said upper stud providing a portion of restricted crosssectional area in the tube constituting a main venturi, said upper studhaving an opening therethrough extending lengthwise in relation to thetube constituting a boost venturi, a lower stud extending down from thecover generally in line with the upper stud to the bottom of the bowl,said lower stud having a recess extending up from its lower end, screwmeans threaded in the lower end of said recess in said lower studthrough a hole in the bottom of the bowl and holding the bowl and coverin assembly, the portion of said recess in said lower stud above saidscrew means constituting a fuel well, a fuel tube extending down fromsaid boost venturi into said fuel well, said screw means being formedfor flow of fuel from the bowl to said fuel well, a throttle in saidtube downstream from said upper stud, said lower stud having an idlepassage extending up from the lower end thereof to idle passage groovingin the top of the cover, said tube overlying said idle passage grooving,said idle passage grooving extending to an idle port in the tube walldownstream from the throttle, and said idle passage in said lower studbeing in communication toward its lower end with the bowl.

2. A carburetor as set forth in claim 1 wherein said screw meanscomprises a tubular screw having a metering orifice at the upper endthereof and a metering valve adjustably threaded in said tubular screwand associated with said orifice.

3. A carburetor as set forth in claim 2 having an idle adjusting screwextending across the tube in line with said idle port, said screw beingthreaded in a hole in the top of the tube and having its lower endassoicated with the idle port.

4. A carburetor as set forth in claim 3 wherein said idle adjustingscrew is engageable by the throttle to determine the full-open positionof the throttle.

5. A carburetor comprising a fuel bowl, a. cover on the bowl, a tubeconstituting a mixture conduit extending across the cover, a first studformed integrally with the cover extending downwardly into the bowl andhaving an axial recess therein extending the length of the stud toprovide a fuel well in communication with the bowl, a second stud formedintegrally with the cover extending upwardly from the cover across thetube through aligned holes in the tube wall to provide a portion ofrestricted cross-sectional area in the tube and having an openingtherethrough extending lengthwise in relation to the tube to provide aboost venturi, means associated with the upper end of said second studfor holding the mixture conduit in assembly with the cover, a fuel tubeextending from the boost venturi into the fuel well for delivery of fuelto said boost venturi, a tubular screw threaded in the lower end of saidrecess through a hole in the bottom of the bowl for holding the coverand bowl in assembly and having a metering orifice at its upper end,said fuel well being constituted by the portion of said recess above theupper end of said screw, and valve means adjustable in said screw formetering flow through said metering orifice, said first stud and saidscrew being formed for flow of fuel from the bowl to said fuel wellthrough said metering orifice under control of said valve means. I

6. A carburetor as set forth in claim 5 having an idle system includingan idle passage in said first stud extending down to the lower end ofsaid first stud, the lower end of said idle passage being incommunication with the bowl.

7. A carburetor comprising a fuel bowl, a cover on the bowl, a tubeconstituting a mixture conduit extending across the cover on top of thecover, an upper stud formed integrally with the cover extending upwardfrom the cover through holes in the tube wall at top and bottom, meanson the upper end of said upper stud holding the tube in assembly withthe cover, said upper stud providing a portion of restricted crosssectional area in the tube constituting a main venturi, said upper studhaving an opening therethrough extending lengthwise in relation to thetube constituting a boost venturi, a lower stud extending down from thecover generally in line with the upper stud to the bottom of the bowl,said lower stud having a recess extending up from the lower end, screwmeans threaded in the lower end of said recess in said lower studthrough a hole in the bottom of the bowl and holding the bowl and coverin assembly, the portion of said recess in said lower stud above saidscrew means constituting a fuel well, a fuel tube extending down fromsaid boost venturi into said fuel well, said screw means being formedfor flow of fuel from the bowl to said fuel well, a thottle in said tubedownstream from said upper stud, said lower stud having an idle passageextending up from the lower end thereof to idle passage grooving in thetop of the cover, said tube overlying said idle passage grooving, saididle passage grooving extending to an idle port in the tube walldownstream from the throttle, said idle passage in said lower stud beingin communication toward its lower end with the bowl, a choke in saidtube upstream from said upper stud, an air bleed hole in the tube walland a passage including grooving in the top of the cover :for bleedingair from upstream of the choke into the fuel grooving from a pointupstream of the throttle and downstream from said upper stud, an airbleed hole and a passage including grooving in the top of the cover forbleeding air from a point upstream of said upper stud and downstreamfrom the choke into the idle passage grooving, and an acceleration portin the tube wall providing for communication from said idle passagegrooving to the interior of the tube when the throttle is open andblocked by the throttle when at idle.

8. A carburetor comprising a fuel bowl, a cover on the bowl, a tubeconstituting a mixture conduit extending across the cover, a stud havingan upper portion extending upwardly from the cover across the tubethrough holes in the tube, means associated with the upper end of thestud for holding the tube on the cover, said stud providing a portion ofrestricted cross sectional area in the tube constituting a main venturiand having an opening therethrough extending lengthwise in relation tothe tube constituting a boost venturi, a choke in said tube upstreamfrom said stud, a throttle in said tube downstream from said stud, saidstud having a lower portion extending downwardly into the bowl with anaxial recess therein forming a fuel well in communication with the bowl,a fuel tube extending from said boost venturi into said fuel well, anidle passage extending from said bowl to an idle port downstream of saidthrottle and including idle passage grooving in the top of the cover, anair bleed hole in the tube wall and an air passage including grooving inthe top of the cover for bleeding air from upstream of the choke intothe fuel well and the idle passage grooving, and an idle air bleed holein the tube wall for bleeding air into the idle passage grow-ing from apoint upstream of the throttle and downstream from said upper studportion.

9. A carburetor as set forth in claim 8 wherein an air bleed hole and anair passage are provided for bleeding air from a point upstream of saidupper stud portion and downstream from the choke into the idle passagegroov- 8 ing and including grooving in the top of the cover, and anacceleration port in the tube wall is provided for communication fromsaid idle passage grooving to the interior of the tube when the throttleis open and blocked by the throttle when at idle.

10. A carburetor comprising a fuel bowl, a cover on the bowl, a tubeconstituting a mixture conduit extending across the cover, a first studformed integrally with the cover extending down into the bowl, meansassociated with the lower end of said first stud for holding the coverand bowl in assembly, a second stud formed integrally with the coverextending upward from the cover across the tube through holes in thetube wall and having an opening therethrough extending lengthwise inrelation to the tube constituting a boost venturi, means associated withthe upper end of said second stud for holding the tube in assembly withthe cover, said second stud providing a portion of restrictedcros--sectional area in the tube, said first stud having an axialpassage for delivery of fuel from the bowl to said boost venturi, thesaid axial passage in said first stud also providing a fuel well incommunication with the bowl, and wherein there is provided a fuel tubeextending down from said boost venturi into said fuel well.

11. A carburetor as set forth in claim 10 having an idle systemincluding an idle passage in said first stud.

References Cited by the Examiner UNITED STATES PATENTS 1,758,954 5/1930Linn 26141 1,857,543 5/1932 Heitger 26'141 2,094,959 10/1937 Pulidori26178 X 2,670,189 2/1954 Phillips 261-41 2,759,716 8/1956 Jones 26 1-412,799,486 7/1957 Teschenclorf et al. 261-4l 2,852,240 9/1958 Goodyear26l41 2,914,307 11/1959 Eickmann 26 l--72 X 3,093,699 6/1963 Demitz261-72 X 3,100,236 8/1963 Ott et al 261-72 X 3,103,544 9/1963 Kalert etal 261-72 X 3,105,861 10/1963 Korte 26172 HARRY B. THORNTON, PrimaryExaminer.

1. A CARBURETOR COMPRISING A FUEL BOWL, A COVER ON THE BOWL, A TUBECONSTITUTING A MIXTURE CONDUIT EXTENDING ACROSS THE COVER ON TOP OF THECOVER, AN UPPER STUD FORMED INTEGRALLY WITH THE COVER EXTENDING UPWARDFROM THE COVER THROUGH HOLES IN THE TUBE WALL AT TOP AND BOTTOM, MEANSON THE UPPER END OF SAID UPPER STUD HOLDING THE TUBE IN ASSEMBLY WITHTHE COVER, SAID UPPER STUD PROVIDING A PORTION OF RESTRICTED CROSSSECTIONAL AREA IN THE TUBE CONSTITUTING A MAIN VENTURI, SAID UPPER STUDHAVING AN OPENING THERETHROUGH EXTENDING LENGTHWISE IN RELATION TO THETUBE CONSTITUTING A BOOST VENTURI, A LOWER STUD EXTENDING DOWN FROM THECOVER GENERALLY IN LINE WITH THE UPPER STUD TO THE BOTTOM OF THE BOWL,SAID LOWER STUD HAVING A RECESS EXTENDING UP FROM ITS LOWER END, SCREWMEANS THREADED IN THE LOWER END OF SAID RECESS IN SAID LOWER STUDTHROUGH A HOLE IN THE BOTTOM OF THE BOWL AND HOLDING THE BOWL AND COVERIN ASSEMBLY, THE PORTION OF SAID RECESS IN SAID LOWER STUD ABOVE SAIDSCREW MEANS CONSTITUTING A FUEL WELL, A FUEL TUBE EXTENDING DOWN FROMSAID BOOST VENTURI INTO SAID FUEL WELL, SAID SCREW MEANS BEING FORMEDFOR FLOW OF FUEL FORM THE BOWL TO SAID FUEL WELL, A THROTTLE IN SAIDTUBE DOWNSTREAM FROM SAID